Tuesday, November 23, 2010

Choosing the Right Lens

Editors note: A customer/blog reader sent us an email asking us to do a post on when to use different types of lenses, or which lenses are best to use when. Before we get into deep explanations and more detailed learning, I want to point out that there isn't ONE lens to use for portrait work, and ONE lens to use for landscape, and so on. While one photographer may use X lens to do their portrait work, another photographer may use Y lens to their portrait work and X lens to do their travel photos. When it comes down to it, it's a matter of personal preference. Yes, certain lenses are better at capturing certain things than others, and understanding how different types of lenses work and what they do will help you to choose a lens that best meets your needs. My personal suggestion for picking a lens is to: 1) do your research/reading (like in the following article); 2) determine your budget; 3) make a list of what lenses you already have; 4) figure out what you want your new lens to accomplish; 5) think about how close or far away from your subjects you like to be when photographing; and 6) weigh your options and the most important aspects in a lens.

Now, if you still need further help picking out a lens, you have a few more options... Ask another photographer who is shooting in the same genre as you (and that you like their work) what they are using. Talk to a sales associate; they can guide you. Purchase a few cheaper used lenses, try them out, and then resell or trade them in for a better version of your favorite one. Rent some lenses and test them out before buying.



Following article by: Arthur Z.

Basic overview of topics covered: lens designs, focal lengths, apertures, and types of lenses (film, digital, fixed or constant aperture, variable aperture, reflex or cat, leaf shutter, macro, micro or close focus, PC, etc).


For most of you that weren't into photography when it was first introduced (about 10,000 AD), the first cameras didn't have lenses attached. The camera lens came about in the early 1600s. But that's another story, so let's jump forward to modern times...

There are two variables that a lens has to control in order help you create great photos. The first factor is the focus. This is done by moving the lens elements (or groups of elements) further or closer to the film plane (the area in the back of your camera that the film lays flat against). I realize that some of you have digital cameras, so for you, this would be where the chip (light gathering sensor) is located. The second factor is how much light goes through the lens. This is controlled by an iris or aperture located inside the lens.

So, what is a normal lens? That depends on which camera that you're using. If you are using a 35mm film camera, this would typically be considered a 50mm. If you are using a medium format camera (2 ¼) roll film camera, this would be somewhere between a 75-80mm lens. If you are using a 4x5 or large format camera that uses sheet film, you might choose a lens somewhere around 200mm as your normal lens. Just as a guide, if you close one eye and look around, that would be close to the magnification and angle of view that a "normal lens" would give you.

How about a portrait lens? For a 35mm film camera, this would be a lens that ranged anywhere from 85mm to 105mm. For a 2 ¼ roll film camera, this might be a 150mm lens. If you have a large format 4x5 sheet film camera, your portrait lens might be somewhere between 350mm and 400mm.

Now, to complete your lens kit, you'll probably want a wide angle lens. For a 35mm film camera, this might be somewhere between a 20mm and a 35mm. For a medium format 2 ¼ film camera, this might be a lens between 85mm and 135mm. For a large format camera, a wide angle may be a 90mm lens (this would roughly be like a 28mm lens on 35mm camera). No, I didn't forget about the fisheye lens, but I would consider that a specialty lens. If you like round images that cover 180 degrees, they give fun results.

Zoom lenses are probably the most popular sold today. If you asked someone 30 years ago if there was a difference in quality between a zoom lens and a fixed focal length lens, they wouldn't hesitate to say yes. They were larger, heavier, more expensive, and not as sharp as fixed focal length lenses. Fixed focal length lenses also had the advantage of being less expensive, smaller, lighter, and having larger apertures. Today, with computer technology, any quality difference between the two types of lenses is minimal, and most people feel that the versatility of having a zoom lens far outweighs the difference there may be in image quality. But of course, some people still swear that prime lenses (or non-zoom) are better.

Constant or fixed aperture compared to variable aperture... Many of you own zoom lenses that have a variable aperture. So what does this mean? Let's take a 70-210 zoom lens that might be an F4.0-5.6. This means that if you set the aperture manually on 4.0 and you zoomed the lens from 70-200mm, even though the lens aperture scale said that the lens was set on 4.0, when you zoomed to 210mm, the actual aperture setting would be 5.6. A constant aperture lens keeps the same aperture setting no matter what focal length that you have zoomed to. Does this make a difference? Yes and no. If the camera was on automatic, the camera would compensate by adjusting your shutter speed to make up for the light loss, and you'd probably never notice the difference. If you are shooting manually, with studio lighting, and/or externally metering, your exposure will be off. If you've determined that 4.0 gives you a perfect exposure, you have the camera set on manual, you take some photos at 70mm, then zoom in and take some at 210mm, the images that were zoomed closer than 70mm will be under exposed. Keep in mind, the aperture change is gradual through the zoom range. With that being said, negative film has a fairly large exposure latitude. Slide film is not as forgiving, and as for digital, yes, you can fix it with editing software. Words of wisdom... the more you can do in your camera, the less you'll have to do in the darkroom, or on the computer later. Variable aperture lenses are generally smaller, lighter, and less expensive than constant aperture lenses.

Reflex, mirror or cat (catadioptric) lenses use mirrors instead of large glass lenses to create high magnification of images. The advantage of these is their smaller size, lighter weight, and lower price. The possible disadvantage is that they are generally made in longer focal lengths (300mm to 1200mm), but have smaller apertures than the conventional refractor designed lenses. They are also “fixed” aperture lenses which means that they don't have an aperture ring. If you buy a 500mm f8 lens, it's a 500mm f8 lens. If you want to change your exposure, it has to be done by inserting neutral density filters in the lens, or by changing the shutter speed of your camera. Although you may find these with lens mounts that will fit on auto focus cameras, they are manual focus lenses. Are the photos any different when taken with these lenses? Yes, if you look close, the blurred background will show small “doughnut rings” of light. Is there a difference in image quality? It depends how critical you are. Most people like the ability to hand hold a 500mm mirror lens. Although you can now do that with Nikon's VR lenses and Canon's IS lenses, you won't believe the size and weight difference.

So what's a leaf shutter lens? You can find leaf shutter lenses made for large format, medium format, and 35mm (size) camera lenses. I used to just say 35mm, but today, with digital cameras, I need to be a bit more specific. Many film cameras used focal plane shutters in them. The limitation of this type of shutter was that it would only synchronize with a flash at slower shutter speeds (1/250th or slower). Lets say you want to take photos outside on a sunny day. You're taking photos of hummingbirds hovering around your bird feeder, and need to use a flash, but you want to shoot at 1/1000th of a second. Go ahead, you've got a leaf shutter built into your lens, and it will synchronize with your flash at any shutter speed.

Macro, micro, close focus, what's the difference? Macro and micro are the same. Close focus or tele macro isn't. Let's compare. First, lets look at the early zoom lenses. If you had an early 80-200mm, 28-200, or other wide range zoom lens, they were great from about 4 or 5 feet on out, but most of the lenses in this range really didn't do a good job of focusing much closer than that. Along came newer designs that are smaller, lighter, and now have close focus. They can actually focus down to 2 or 3 feet. They're amazing. You could shoot flowers and small objects without changing lenses. If you want a true macro lens, you probably won't be buying a zoom lens, you'll be buying a fixed focal length lens (like a Nikon 60mm Macro). So what makes this lens so special? It's a “flat field” lens. If you take a photo of a page of newspaper with a flat field lens, it will be sharp from edge to edge. If you took the same photo with a zoom lens with “macro” or “close focus”, you would probably see that the center of the image is sharp and the top, bottom, and sides would be soft. This is because you most likely took your photos with a “curved field” lens. There are a few exceptions to this, but they're very expensive.

What's a PC (perspective control) or tilt-shift lens? It's a lens that can change the perspective to your photos. Have you ever taken photos of a large building that appears to curve at the top or sides when you're using a wide angle lens? How about taking that photo and having all of the sides being straight? These lenses have a very complex design that allows it to almost break in half and have the front half shift up, down, right or left. For those of you that have used a 4x5 large format camera, one of the key features (besides the larger negative) is its ability to have swings, tilts and shifts which allowed you to correct the distortion (or plane of focus). Many photographers are using tilt-shift lenses to get artsy with, in addition to using it for correcting purposes.

Yes, tele converters, 1.4X converters, 1.7X converters, and 2X converters are lenses, but I would consider them specialty lenses. In other words, they modify the performance of other lenses that they are attached to. The good news is that most converters are usually less expensive than most lenses. The bad news is that there are quite a few converters out there that will reduce the quality of the lenses that you use them with. A good rule of thumb is to stay with a name brand converter. Another consideration would be the light loss. A 2X converter will reduce the amount of light that enters the camera by ½. This means that some camera/lens combinations will not work with a converter. When in doubt, call your friends at KEH to confirm.

One of the most important factors in your lenses should be quality. If your main concern is getting sharp, colorful, crisp (good contrast) images, you'll need to invest in quality glass. Remember that as with many things in life, including lenses, you get what you pay for. Most manufacturers make several different grades of glass. There's glass for consumer use, and glass for professional use. Canon's premium optics will be made of “L” (low dispersion) glass, while Nikon calls their premium glass “ED” (extra-low dispersion). One other thing to look for would be lenses that have the “APO” designation. So what's an APO lens? It stands for apochromatic, and what it does is pretty interesting. Remember when you were in science class and the teacher put a prism in sunlight? In one side comes white light, out the other comes a rainbow of colors. Pretty amazing stuff. If you had a good science teacher, they told you about light having different wave lengths and focusing in different planes. Long story short, an APO lens makes sure that all of the colors in the spectrum focus with the same intensity on your piece of film (or sensor) so that your finished image has true colors (not too warm or cold).

Another very important factor to consider is lens compatibility. We covered this topic in depth back in September. Broken down into 4 parts: Part 1-Digital camera sensor sizes (full frame vs. APS-C), Part 2- Manufacturer lens vs. non-mfg. lenses, + more compatibility considerations, Part 3- Finding a lens on our website, and Part 4- crop factor.

And finally, we still haven't covered every single thing in this post, but we have talked about other lens topics before. If you'd like to read more about lenses, here's where to go next:
- For info. on shooting macro and close up
- For info. on IS (image stabilization) and VR (vibration reduction)
- For lens problems: Lens sep, messy lenses and picture quality, the bottom shadow